PAUL SQUIRE PHOTO | Waste water being aerated in one of the two 750,000-gallon treatment tanks at the Riverhead Sewer District plant. With the required plant upgrades, the treated water would be pumped through a high-tech filtration system.

The applications were filed before the deadline earlier this month, said the town’s sewer superintendent, Michael Reichel.

The town’s permit for the sewer district plant — located on River Road near the county’s Indian Island Country Club — requires the town to complete an upgrade by January 2014 that will meet new water quality standards.

Until all funding is secured, the district will have to file for an extension on the deadline for the upgrades, Mr. Reichel said.

Suffolk County Planning and Economic Development officials are reviewing the grant proposals and will recommend applicants to the county Legislature.

Mr. Reichel said he was unsure when the county would choose who to award the grant to, though he was hopeful the process would be quick as long only a few applicants applied.

The sewer district currently has about $2.1 million available through a state grant, another $700,000 set aside in a nitrogen-mitigation fund and a remaining district fund balance that can be applied toward the upgrade, Mr. Reichel previously told the News-Review.

The district is still about $12 million short of what’s needed.

If the town can’t secure county money, the assessed value portion of customers’ sewer tax bills would have to jump by more than 522 percent, good for a jump of about $35 a year to $215 a year for an average homeowner in the sewer district.